This invention relates in general to the field of secure communication, in particular to secure communication between digital and analog communication systems.
One problem with today""s wireless communication systems is security of the information communicated over radio frequency (RF) links. Typical digital systems that provide some security, for example, encrypt the air interface between a mobile handset and a base station. The terrestrial portion of the connection is not encrypted so end-to-end security is not provided. These digital networks that provide security, do not allow for the use of user specific security. For example, digital systems that use standard encryption algorithms, such as GSM""s A3/A8 encryption algorithm, do not support substitution of these standard algorithms with custom or user specific algorithms. Accordingly, customers must rely on the standard encryption algorithms provided by the network with reduced confidence and the risk that the security may be compromised.
Another problem with existing digital networks is that calls originally in clear-voice mode can not be transferred easily to secure voice or data mode without establishing a new link through the network. Another problem with existing technology is that large organizations do not have the ability to provide an interworking function between a digital network and the organization""s protected private PBX. The organization must connect between the digital network and their private PBX through the PSTN.
Thus what is needed are a method and apparatus for interfacing a digital communication system with the PSTN and providing secure communications over a digital link. What is also needed is a method and apparatus that allows for user specific security through a digital network and provides for the communication of voice followed by data. An apparatus or method that provides for the communication of voice followed by the data, for example, has an advantage of allowing a call to be placed in the clear mode and then converted to an end-to-end secure call.
What is also needed are a method and apparatus that provides an interworking function allowing a large organization to connect between a digital communication system and the organization""s protected private PBX.